Information to support an Application for Marine Construction Projects in the Territorial Sea and UK Controlled Waters Adjacent to Scotland under the Marine and Coastal Access Act 2009 Phase 1 Meteorological Mast Installation Round 3 Zone 2 Firth of Forth Offshore Wind Farm Development
Contents 1 Project title... 1 2 Applicant... 1 3 Description of project... 1 3.1 Detailed schedule of work... 1 3.2 Type of work proposed... 1 4 Location of the project... 4 4.1 Location of the Seagreen Firth of Forth Zone... 4 4.2 Meteorological mast installation... 4 5 Method statement... 7 5.1 Meteorological mast foundation... 7 5.2 Meteorological mast topside... 7 5.3 Installation method... 8 5.3.1 Preferred method using jack up rig... 8 5.3.2 Alternative method use of crane barge... 8 6 Consultation with conservation bodies... 11 7 Environmental appraisal... 12 7.1 Marine mammals... 12 7.1.1 Cetaceans... 12 7.1.2 Pinnipeds... 14 7.1.3 Consideration of potential impacts on marine mammals... 19 7.2 Sediment processes... 24 7.2.1 Baseline... 24 7.2.2 Consideration of potential impacts... 25 7.3 Seabed habitats and species... 26 7.3.1 Baseline... 26 7.3.2 Consideration of potential impacts... 30 8 Summary... 31 9 References... 32 i.
1 Project title Round 3 Zone 2 Firth of Forth Offshore Wind Farm Development Phase 1 meteorological mast installation. 2 Applicant Company Seagreen Wind Energy Limited 55 Vastern Road Reading Berkshire RG1 8BU. Company Registration No: 06873902 3 Description of project 3.1 Detailed schedule of work Transport and installation of one meteorological mast, hereafter referred to as the met mast, into the Phase 1 development area of the Firth of Forth Round 3 Offshore Wind Zone is planned for a period between June 2012 and September 2012. Demobilisation of the installation vessel will be immediately after completion of all works in 2012. A draft detailed schedule of works is provided in Figure 4.1 below. The key work elements can be summarised as follows: Mobilisation to site by construction vessel up to one week; Positioning of installation vessel on site (positioning of legs on seabed) up to 4 hours; Installation of met mast foundation up to 2 days; and, Installation of topside structures up to 2 weeks. It is important to note that the programme of works provided is based upon the best available data and may change to respond to conditions at the time of installation. 3.2 Type of work proposed The work proposed is the installation of one met mast at one of two potential locations. Two potential installation locations have been selected and both of these have been assessed. However, only one of these two locations will be used. A final [1]
site selection will be made following the completion of feasibility studies at each location. An installation vessel will move to the agreed met mast installation location carrying the foundations and topside structures of the met mast and fix its position. A suction caisson foundation will then be installed into the seabed. After installation of the foundation, the topside structures will be installed on top of the foundation by the same installation vessel. Details of the locations and construction methods are provided in section 6 of this report. The planned met mast deployment is for 20 25 years, with a review of the selected location based on data collected and the final wind farm layout after an initial 5 years. [2]
Figure 4.1 Draft schedule of works [3]
4 Location of the project 4.1 Location of the Seagreen Firth of Forth Zone Seagreen Wind Energy Limited, hereafter referred to as Seagreen, has been awarded the rights to develop a number of offshore wind farms in the Firth of Forth Round 3 Zone, hereafter referred to as the Zone, by The Crown Estate, under the third round of the offshore wind licensing arrangements (commonly referred to as Round 3). Seagreen has a Zone Development Agreement with The Crown Estate which sets the contractual programme milestones for the development of the Zone and identifies a target generation capacity of up to 3.465 Gigawatts to be delivered across the Zone. The Zone lies approximately 25km off the south east coast of Scotland. Seagreen intends to progress the development of wind farm projects in the Zone in three separate development phases and is currently focussing on the development of the Phase 1 projects, Seagreen Alpha and Seagreen Bravo. The location of the Zone and the Phase 1 area are shown in Figure 5.1, below. The Phase 1 area is located in the north of the Zone, and covers an area of approximately 597km 2. The area lies approximately 25km from the Angus coast. The proposed installed capacity for the Phase 1 projects is 1.075 Gigawatts. Subject to obtaining the necessary approvals, commencement of construction works on Phase 1 is planned for 2015. A Phase 1 Scoping Report was submitted to the Scottish Government in July 2010 and the Scottish Government (through Marine Scotland) responded with its scoping opinion on 27 th January 2011. Applications for development of the Phase 1 projects will be submitted in 2012. There are two Scottish Territorial Waters (STW) wind farm developments adjacent to the Firth of Forth Zone; the Neart na Gaoithe and the Inchcape wind farms, shown in Figure 5.1, below. 4.2 Meteorological mast installation This report is provided in support of an application for a Marine Licence (Application for Marine in the Territorial Sea and UK Controlled Waters Adjacent to Scotland) under the Marine and Coastal Access Act 2009, as regulated by Marine Scotland under the Marine (Scotland) Act 2010. One met mast will be required in Phase 1 of the Zone, to measure the wind speed and enable estimates of potential energy outputs from the wind farm. The proposed locations for the met mast are shown in Figure 5.1, below, and coordinates are provided in Table 5.1. Following best practice, Seagreen will undertake a detailed survey for unexploded ordinance (UXO) at the proposed [4]
locations. Although preliminary risk assessments do not suggest the presence of potential UXO targets, in the unlikely event that detailed survey identifies targets at the proposed locations, it may be necessary to micro site the met mast locations, varying the final location by a few tens of metres. Any change would be agreed with Marine Scotland Licence Operations Team (MS LOT) in advance of installation to allow the licence to be revised accordingly. Table 5.1 Coordinates of the proposed met mast locations Location Name Easting (m) Northing (m) Latitude Longitude BH03 563075 6274624 56 36.69587 N 1 58.34129 W BH 08 582990 6267852 56 32.86000 N 1 39.00847 W The locations provided in Table 5.1 were selected based on a detailed assessment of the Phase 1 area geotechnical survey results. Seagreen expects to confirm the preferred met mast location on contract award early in 2012. [5]
Figure 5.1 Seagreen Phase 1 area and STW site locations, showing the proposed met mast locations [6]
5 Method statement 5.1 Meteorological mast foundation Key aspects of the foundation are summarised below: The foundation will be a steel suction caisson, hereafter referred to as the caisson foundation; The caisson foundation type to be used, is shown in Figure 6.1, below; The design of the caisson foundation is still being developed; however, current designs are advanced and allow for a caisson diameter of up to 15m. This may vary slightly in the final design, but will not exceed 30m; Once in position on the seabed, water will be pumped from inside the foundation to draw the caisson foundation into the supporting sediment via suction ; The skirt of the caisson foundation will be fitted with a seawater injection system to ease the movement of the gravity base into the seabed; Current design anticipates the embedding of the caisson foundation to a depth of approximately 12m. A 12m high caisson with diameter of 15m will enclose a volume of sediment of up to 2,124m 3 ; Above the caisson foundation the supporting structure of the foundation extends upwards to the surface; and Estimated foundation (in air) weight is 450 tonnes. 5.2 Meteorological mast topside Key aspects of the topside are summarised below: The mast will extend to a maximum height of 120m above lowest astronomical tide (LAT); The mast will support a variety of meteorological data collection equipment; The mast will support navigation lighting; The mast will be fitted with a fog detection and signalling system; The mast will be fitted with a radar reflector; The mast will be powered via a renewable energy source and batteries; and [7]
The mast will be painted and otherwise marked according to the requirements of the Northern Lighthouse Board and Maritime and Coastguard Agency, with any modifications agreed with those parties and Marine Scotland. 5.3 Installation method 5.3.1 Preferred method using jack up rig Key aspects of the method statement include: The jack up rig Brave Tern or her sister ship Bold Tern will move to site under its own power. The rig s dynamic positioning (DP) system will be used to hold position for a limited period while the rig s legs are lowered to the seabed. This procedure is likely to take approximately 1 hour, but may take up to a maximum of 4 hours; The rig has 4 legs terminating in spud cans, as is normal for most jack up barges, with a total seabed footprint of 106m 2 for all 4 cans combined; The rig will undertake installation of the met mast foundation followed by installation of the met mast topside; The rig is the only vessel required for the installation; The seabed installation of the suction caisson foundation will be undertaken using a suction method. No piling works of any type will be required; Installation time for the suction caisson foundation is estimated to be up to 4 days; and After completion of the suction caisson foundation installation, the met mast installation time is estimated to be up to 2 weeks. 5.3.2 Alternative method use of crane barge The proposed jack up rig, the Brave Tern, is currently under construction and is at the time of writing, on schedule for delivery in time to undertake Seagreen s met mast installation. Seagreen has a contract with the installation company that requires them to use the Brave Tern to install the temporary met mast. It is Seagreen s preferred methodology to use a jack up rig to undertake installation; however, any unexpected difficulties with the delivery of Brave Tern and a subsequent failure to find a suitable replacement within the proposed project timeframe, would necessitate a change in methodology. The alternative method identified would likely be use of a crane construction barge, with DP systems to provide and maintain the required positioning of the barge. DP systems would be [8]
required for the full duration of the met mast installation, including both foundation and topside installation. [9]
Figure 6.1 Proposed suction caisson foundation type [10]
6 Consultation with conservation bodies Seagreen has undertaken extensive consultation on its proposals for the development of Phase 1. The consultation included consideration of a temporary met mast installation, as part of the Phase 1 EIA scoping exercise. The Phase 1 Scoping Report was previously issued to Marine Scotland and made available to a wide range of consultees and can be downloaded from the Seagreen website (http://www.seagreenwindenergy.com/home.asp). The responses from consultees are all held by Marine Scotland. Seagreen has also undertaken a screening consultation exercise for the proposed met mast installation. Comments have been received from Marine Scotland, Joint Nature Conservation Committee, Civil Aviation Authority, Maritime and Coastguard Agency, Northern Lighthouse Board, the National Air Traffic Control System and the Ministry of Defence. In addition, as part of ongoing consultation with fisheries representatives, the need for met masts and their potential locations has also been discussed. All relevant comments from regulator and consultees been incorporated into this document and method statement. [11]
7 Environmental appraisal An appraisal of 3 key potential environmental receptors has been undertaken in support of this application. These receptors have been chosen to encompass potential impacts on the physical seabed environment; key seabed habitats and species; as well as potential impacts on marine mammals encountered within the proposed met mast deployment area. The appraisal addresses matters raised in the responses to the screening consultation. The receptors considered within this report and the reasons for their consideration here are summarised as follows: Marine mammals including cetaceans (which are all European Protected Species (EPS)) and pinnipeds. Seagreen is aware of the potential impacts of works at sea on marine mammals via noise, vibration, disturbance and physical injury, both through the responses to the Phase 1 Scoping Report and the later screening responses for this met mast application; Seabed habitats and species including benthic habitats and sand eels. As a result of responses to the Phase 1 Scoping Report, Seagreen is aware of the importance benthic habitats play in the wider ecology of the Phase 1 area in particular those supporting sand eels (an important food source for birds, marine mammals and wider fisheries); and Sediment processes The importance of sediment processes has been identified in responses to the Phase 1 Scoping report. Seagreen is currently discussing approaches to the assessment of impacts on sediment processes with Marine Scotland and the installation of the met masts will be the first potential impact on sediment processes from this project. 7.1 Marine mammals The review of existing marine mammal data covering the entire Zone, undertaken by SMRU Ltd on behalf of the Forth and Tay Offshore Wind Developers Group (FTOWDG) have been used in support of this report. These reports (SMRU 2011a and SMRU 2011b) are currently in preparation. 7.1.1 Cetaceans Species present Six cetacean species occur frequently within the outer Firth of Forth region; harbour porpoise Phocoena phocoena; white-beaked dolphin Lagenorhynchus albirostris; Atlantic white-sided dolphin Lagenorhynchus acutus; orca Orcinus orca; bottlenose dolphin Tursiops truncatus; and minke whale Balaenoptera acutorostrata (Hammond [12]
et al. 2004). These species are all expected within the Phase 1 area and the wider Zone. Seagreen has gathered 24 months of marine mammal sightings data during ongoing monthly boat-based surveys across the entire Zone. The 2 year survey programme was completed in November 2011, with analysis of the data by SMRU Ltd ongoing and due for completion in early 2012. Cetacean species recorded during boat-based surveys include harbour porpoise, white-beaked dolphin, white-sided dolphin, common dolphin and minke whale. As part of the aerial bird surveys commissioned by The Crown Estate in 2009/10, sightings of marine mammals were recorded. Seagreen, via FTOWDG, has sought to have these data analysed alongside Seagreen s boat-based survey data (mentioned above). An initial breakdown of cetacean sightings beyond 12 nautical miles (nm) is provided in Table 8.1, below. Table 8.1 Summary of cetacean records from aerial surveys outside 12 nm. Species Summer Winter Sighting totals Bottlenose dolphin 1-1 Harbour porpoise 26 2 28 Long-finned pilot whale - 2 2 Minke whale 1 1 2 White-beaked dolphin 18-18 Large cetacean 2 1 3 Small cetacean 21 1 22 Cetacean 2-2 Total 44 7 78 Relative abundance and distribution A number of cetaceans, including toothed and baleen whales, are believed to be present within the Zone based primarily on SCANS II data. This view is supported by the initial analysis of both Seagreen boat survey data and The Crown Estate aerial data outlined earlier in this section. [13]
Bottlenose dolphins are believed to be largely distributed in inshore waters, with limited presence in offshore areas, including the Zone. Recent data showing distribution of bottlenose dolphins in the Tay area, close to the Zone, are shown in Figure 8.1. This is derived from boat based photo identification data collected by SMRU in June to August 2009 and June to September 2010. Figure 8.1: Location of bottlenose dolphin encounters (blue=2009 and red=2010) in the Forth and Tay region. (Source:- SMRU Ltd 2011a) In figure 8.1 it can be seen that distribution is focussed on inshore areas, and this is supported by the scarcity of sightings for bottlenose dolphin in the Zone (see Table 8.1). 7.1.2 Pinnipeds Species present During the boat-based surveys commissioned by Seagreen both grey seal and harbour seal were recorded. As detailed in section 8.1.1, these data are currently being analysed by SMRU Ltd. An initial review of aerial survey data collected by The Crown Estate during 2009/2010 also recorded 79 seals (both grey and harbour) outside 12nm, with 74 recorded during the summer months and 5 during winter months. [14]
Relative abundance and distribution The nearest grey seal haul outs are to the west of the Phase 1 area, at Abertay, and to the south west at the Isle of May. Both are over 50km from the proposed met mast locations. Grey seals are known to forage up to 145km from their haul out sites and it is therefore possible that animals may be in the vicinity of the met mast during the winter pupping season (October to January) and the spring moult (February and March (SCOS, 2009). Harbour seals range less widely than grey seals, generally within 60km of their haul outs (McConnell et al 2004). The nearest breeding colony at Tentsmuir is more than 50km from the proposed met mast locations. The recent Seagreen monthly boat survey data appear to show harbour seal sightings across the Zone are low compared to grey seal sightings and appear to be largely confined to the south of the Zone. Seagreen, as part of the Forth and Tay Offshore Wind Developers Group (FTOWDG), has commissioned SMRU Ltd to undertake analysis of existing satellite and telemetry data for grey seals and harbour seals. This includes consideration of the following: Harbour seals: o o 25 animals captured in Firth of Tay and Eden Estuary SAC between November 2001 and July 2003; 4 in Eden Estuary May 2008; and o 6 in Eden Estuary in 2011. Grey seals: o 9 tagged at Abertay and 10 at Farne Islands 2008; o 64 tagged at various locations on the UK East Coast 1991-2007; o 21 post-weaned pups tagged at Isle of May 2001/2002. While this data has already been subject to a certain degree of analysis as part of the UK Offshore Energy Strategic Environmental Assessment (SEA) programme, further analysis provides detailed understanding of the at-sea usage within the Zone. The information from an interim note provided by SMRU Ltd (SMRU a & b, 2011 in prep) is outlined below. A buffer was generated which extends 100km from the boundary of the Firth of Forth Zone and STW wind farm developments. Data from a tagged animal are presented only if the animal was recorded inside the buffer area at anytime during its deployment. [15]
Adult grey seals There were 92 tagged adult (age one year and above) grey seals which entered the 100km buffer area. Animals were shown to use the Firth of Forth Zone and surrounding area extensively. Figure 8.1, shows the movements of seals across the study area and it can be seen that there are concentrations of slow moving seal activity in the north of the Zone, including the Phase 1 area, with a particular focus on the Scalp Bank, to the west of Phase 1, indicating possible foraging activity. Figure 8.1 The locations of adult grey seals in the Firth of Forth Region with locations classified by speed (Source:- SMRU Ltd 2011b). Grey seal pups There were 30 grey seal pups tagged at breeding colonies within the buffer area, 9 of these pups were tagged on the Farne Islands (1993-1994) and 21 on the Isle May (2001-2002). The animals were shown to use areas within the Zone and beyond, with Figure 8.2 showing only slightly higher levels of potential feeding activity within Phase 1, than elsewhere in the Zone and wider Firth of Forth area. [16]
Figure 8.2. The locations of grey seal pups around and inside the Zone with locations classified by speed (Source:- SMRU Ltd 2011b). Harbour seals - adults, pre 2011 31 of the tagged adult harbour seals were recorded at locations inside the 100km buffer area. All of these animals were tagged within the buffer area. Figure 8.3 shows the tagged animals using the Zone and areas beyond extensively, but with clear concentrations of feeding activity within the Phase 1 area. These data indicate that the Phase 1 area is important for adult harbour seals as a feeding resource. [17]
Figure 8.3. The locations of adult harbour seals (2001-2008) around and inside the potential wind farm areas with locations classified by speed (Source:- SMRU Ltd 2011b). Harbour seals adults, 2011 Five tags were deployed by SMRU in 2011 on harbour seals in Eden estuary, to the west of the Zone. Figure 8.4 shows animals using the western parts of the Zone, but with no use of the Phase 1 area. Areas of activity lie to the south and west of Phase 1. [18]
Figure 8.4. The locations of adult harbour seals (2011) around and inside the potential wind farm areas with locations classified by speed. Harbour seals pups Very few harbour seal pups have been tagged in the UK and none in the East coast of Scotland. There were no locations of tagged harbour seals pups in the buffer region. 7.1.3 Consideration of potential impacts on marine mammals Risk Assessment for European Protected Species (EPS) All cetaceans are listed under schedule 2 of Council Directive 92/43/EEC on the conservation of natural habitats and of wild fauna and flora, otherwise known as the Habitats Directive, as European Protected Species (EPS). The JNCC, Natural England and CCW (October 2010) produced draft guidance concerning the new Regulations The protection of marine European Protected Species from injury and disturbance - Guidance for the marine area in England and Wales and the UK offshore marine area (JNCC et al, 2010), on the deliberate disturbance of marine EPS, which provides interpretation of the regulations in detail. The UK nature conservation agencies and environmental regulators suggest a risk assessment approach when considering potential for impacts on marine EPS from developments in the current draft guidance. The risk assessment process detailed in the draft guidance follows a two-step process: 1. assessing the likelihood of offence, and 2. [19]
whether a licence should be sought. This is illustrated in Figure 8.6 below, a flowdiagram (from JNCC et al 2010), summarising the approach recommended. Figure 8.6 Summary of EPA risk assessment process (JNCC et al, 2010 draft) The guidance draft (JNCC, 2010) states that Any risk assessment should start by considering whether any injury and/or disturbance offences are likely, based primarily on the nature, the duration and extent of the activity(ies). While a short-term operation affecting a small area could result in an injury offence, it is more likely that a disturbance offence would occur as a result of a long-term operation or combination of operations. The first stage of the 2 stage risk assessment process for EPS is followed below. [20]
Risk assessment stage 1 Assessment of the likelihood of an offence The potential for met mast installation to disturb EPS through noise or physical activity must be considered, for both the preferred installation method (using a jack up rig) and worse case method (using a crane barge). Although no specific advice regarding jack up or DP barge operations, nor the potential disturbance from suction caisson installations, are provided in the draft JNCC guidance (JNCC et al 2010), it is possible to draw comparisons with other, comparable, activities. It is necessary to consider the nature of both the species present in the potential area of impact and the nature of the potential impact in order to assess the likelihood of an offence (deliberate injury or disturbance to EPS) occurring. Stage 1 can therefore be separated into two elements: Nature and presence of EPS; and, The potential of an activity to cause a disturbance offence. Nature and presence of EPS The data presented in section 8.1.1, above, suggest that a number of EPS (cetacean species) are present within Phase 1 and could therefore be vulnerable to potential disturbance impacts caused by operations associated with the met mast installation. The cetacean species present will be sensitive, to varying degrees, to activities producing large amounts of noise, such as piling or blasting activities. Potential for met mast installation to cause a disturbance offence Three aspects of the planned activities need to be considered and assessed in order to determine the potential to cause disturbance, these are: Consideration of alternative sites and installation methods; The likelihood that the sound experienced by the animals exceeds injury and/or disturbance thresholds; and, Likelihood of exposure of EPS to disturbance. Each of these three aspects is considered in turn below. Consideration of alternatives A number of potential met mast locations have been considered within Phase 1. Two potential sites are currently proposed, both are considered most suitable for installation, based on best current knowledge, and either BH3 or BH8 could be taken forward, each a possible alternative for the other. In addition, in identification of the [21]
two alternative sites (BH3 and BH8) proposed, a series of other poitential locations have been considered, with borehole data from 10 potential met mast locations in Phase 1 considered. The alternative installation method to that proposed (suction caisson foundation) would be piling. This method has successfully been used for met masts installed on other Round 1, 2 and 2.5 sites. It is also the preferred method of installing foundations for offshore wind turbines. However, piling has been identified by regulators as a potential impact on EPS in terms of noise impacts. Seagreen's proposed alternative approach to installation, using a suction caisson foundation, with no requirement for piling, is considered less likely to have an impact for met mast installation. Injury or disturbance thresholds The installation of the met mast will result in noise and disturbance associated with both the operation of the installation vessel and the installation of the suction caisson itself. The operational noise of the installation vessel (the jack up rig) will be present at the installation location for a short period of time, estimated as approximately 2 weeks. The noise and physical disturbance levels associated with the vessel can be assumed to be reasonably similar to other vessels (ships) of a similar size, and in the case of shipping activity the JNCC guidance considers that It is most unlikely that a passing vessel would cause more than trivial disturbance. It is the repeated or chronic exposure to vessel noise that could cause disturbance in the terms of the Regulations. The Phase 1 area is regularly transited by a full range of vessels from tankers to fishing vessels, and can be considered a major shipping route. It is reasonable to assume that operation of the jack up vessel on site for 2 weeks, plus mobilisation and demobilisation time is negligible by comparison and therefore unlikely to contribute significantly to noise or disturbance within the Phase 1 area. No data are available for the noise generated by the installation of a suction caisson foundation; however, comparisons can be drawn with other similar operations for which data are available. The JNCC guidance suggests that for operations such as dredging of maintenance channels the risk of injury is considered negligible and potential for disturbance is limited to operations of durations that are likely to cause chronic exposure. The period of time required for installation of the suction caissons is estimated as 2 days, after which the installation of the topside of the mast will commence. It is unlikely that this duration of installation is sufficient to result in chronic exposure to the anticipated noise levels generated. During the operational phase the met mast will require limited maintenance and servicing activity which is expected to be achieved through boat access. This low intensity maintenance activity is not considered likely to pose a disturbance risk to marine mammals. [22]
Likelihood of EPS exposure to disturbance The short period of time required for the installation of the proposed met mast, approximately 2 weeks, combined with the low impact level of the suction caisson foundation installation technique means that the proposed met mast installation has low potential to damage or disturb EPS (as outlined in Figure 8.6) and that there is negligible risk of an offence. On the basis of the low potential to damage or disturb of the proposed works, it is considered that there is negligible risk of the proposed installation causing an offence under EPS legislation. Based on the risk assessment process outlined by JNCC no license to disturb is required and therefore no further risk assessment (stage 2) is necessary or appropriate. HRA issues - connectivity of Eden Estuary SAC seals and met mast deployment area Based upon the data presented in section 8.1.2, it can be seen that harbour seals from the Eden Estuary SAC may potentially be present at the met mast locations during installation (see Figure 8.4). However, the limited time period of the operation and the absence of activities generating large amounts of noise all indicate that any potential for impact is negligible. Approach to mitigation for dynamic positioning (DP) use during installation In its letter of 6 May 2011, Marine Scotland asked for a mitigation plan for avoiding impacts marine mammals when using DP vessels to be provided with the application. Concerns have been raised in relation to a possible link between the use of certain types of vessel positioning thrusters (in particular cowled propellers and thrusters), potentially used during marine construction and a recently identified incidence of injuries to harbour and grey seals (Thompson et al, 2010). There is some proposed use of DP during all of the proposed installation methods, with the scale of DP use varying from up to 4 hours using the preferred jack up method, to potentially 2 weeks using the worse case scenario of the DP crane barge method. A DP mitigation plan will be prepared for both installation options. Seagreen has committed to the development of a strategy of appropriate scale and will submit a DP mitigation plan to Marine Scotland for agreement prior to deployment. Key measures of any DP mitigation plan may include: [23]
Seagreen will ensure that vessel operators are aware of concerns regarding potential impacts of DP systems on seals, with contractors required to investigate mitigation such as use of guarded thrusters or methods for alteration of the noise signature of thrusters; The operators will seek to minimise the use of DP where possible, while maintaining vessel safety at all times; Presence of marine mammal observers (MMOs) on board the jack up or DP barge, maintaining watch for marine mammals during the time the vessel is on station during installation; Protocol to delay commencement of DP activation (delay of foundation deployment operations) for a period of time if marine mammals are observed on site prior to DP activation; and Ongoing recording and monitoring of marine mammal activity throughout foundation deployment, and recording of any potential incidents. 7.2 Sediment processes 7.2.1 Baseline Water depths across the Phase 1 area generally range from 40m to 60m below LAT. Water depths shallow to a minimum depth of approximately 32.5m below LAT over the Scalp Bank, in the east of the Phase 1 area (Figure 5.1). A geophysical survey of the Phase 1 area was conducted by GEMS Survey Ltd and reported in 2010. The survey provided detailed information on: Sea bed topography and morphology and identified the nature of the seabed sediments, in particular the height, length and slopes of sand-waves; Sub-bottom geology to a depth of approximately 70 metres below seabed; The location, extent and nature of wrecks, debris on seafloor, rock outcrops, other cables, pipelines etc; and Limited re-interpretation of the gathered acoustic (sidescan sonar) data to determine seabed types by means of an Acoustic Ground Discriminating System (AGDS) supported by sediment grab samples. The maximum water depth recorded by the survey was 85m below LAT to the north west of the Phase 1 area. During the survey no very steeply to extremely sloping areas were identified. There are limited areas of steeply sloping seabed. The majority of the site is summarised as slightly sloping. [24]
The survey identified three main seabed features: Megaripples; Sandwaves; and, Boulder fields. The seabed characteristics encountered during the survey indicate that the majority of the site is subject to sediment transportation. The dominant flow pattern is subparallel to the coastline in a north-northeast to south-southwest (and reciprocal) direction with tidal flow. Currents are strong enough to move and have the potential to erode medium sand grade material. Over the Scalp Bank in the mid-west area, Holocene sediments are subject to erosion and have gradually abraded away; this has led to widespread exposure of boulders at the surface. The boulders are likely to be Quaternary glacial deposits. This process of erosion and exposure has led to isolated boulders and boulder fields being prevalent across the site. Boulder clusters are identified along with areas of widely dispersed boulders in the northern and central parts of the survey area. The maximum recorded size of a single boulder was 4 x 5 x 0.5m and the maximum recorded area of a single boulder cluster field was 0.5km square. Boulder clusters identified in the southern part of the Phase 1 area are not as large as those identified in the northern part. Megaripples are dominant across much of the site and are indicative of sediment transport. The crests of these ripples are orientated perpendicular to the coast line, indicating sediment movement parallel to the coast. Bedforms are generally symmetrical indicating no dominant direction of flow. The height of megaripples is generally less than 0.5m, larger megaripples have gently sloping sides. In the west of the Phase 1 area, large isolated sandwave features are observed with approximately the same orientation as the megaripples. These have a maximum height of 10m with steeply sloping sides. 7.2.2 Consideration of potential impacts Hydrodynamic regime The effects of offshore wind farm structures on wave energy and form has been studied at both Round 1 and Round 2 sites. These studies have concluded that there would not be any significant impacts, either alone or in combination (CEFAS, 2005). Therefore, any potential effects to wave climate during the operation of the wind farm are expected to be restricted to the wind farm site and are not considered to be significant. Potential effects resulting from the presence of turbine or met mast foundations (both singularly and collectively) on the local tidal regime are not thought likely to be significant in either the near or far field, based on findings reported in site [25]
specific studies carried out by CEFAS (2005) and reported in published Environmental Statements for other offshore wind developments. Geomorphology and sediment transport: Site specific monitoring studies undertaken by CEFAS (CEFAS, 2005) and industry studies (ABPmer, 2005) have shown that offshore wind farms will have limited effect on sediment transport within the array area and beyond, as long as the turbine and other structures foundations are adequately spaced. Highly localised change in sediment transport is possible around individual foundation structures, but is not considered to represent a significant effect. Scouring may occur around foundations and other ancillary structures and this has the potential to affect localised morphological processes. However, given the localised nature of scouring effects and the mitigation measures available to reduce the extent of scour, any resultant changes in morphological conditions are unlikely to be significant. 7.3 Seabed habitats and species 7.3.1 Baseline In addition to the geophysical survey data collected by GEMS in 2010, a campaign of benthic sampling has also been undertaken across the Phase 1 area by the Institute of Estuarine and Coastal Studies (IECS), involving the collection of infaunal and sediment character samples from 150 locations, 50 trawls for epi-benthos and 50 video trawls. The benthic survey effort was directed by Royal Haskoning, based on initial findings of the geophysical survey, and the results were used to inform seabed habitat mapping work undertaken by Envision Mapping Ltd. A series of seabed maps have been produced detailing the seabed sediment types across the Phase 1 area, the distribution of habitats and species and the suitability of the seabed across the site as sand eel habitat. The last element, sand eel suitability, was derived using data published by Greenstreet et al, 2010, based upon studies undertaken within the wider Firth of Forth area, including much of the Zone. Maps showing the outcome of the various mapping exercises undertaken are provided in Figure 8.7, seabed sediment, Figure 8.8, seabed habitats and species, and Figure 8.9 sand eel habitat suitability. [26]
Figure 8.7 Distribution of seabed sediment types in Phase 1, with met mast locations shown [27]
Figure 8.8 Seabed habitat and species within Phase 1 with met mast locations shown [28]
Figure 8.9 Seabed sandeel suitability [29]
7.3.2 Consideration of potential impacts The met mast locations do not have the potential to impact areas of significant conservation interest. One of the potential met mast locations (BH08) is within a large area of sandy gravel characterised by the worm Sabellaria spinulosa, while the other (BH03) lies on the edge of an area of gravel and cobble supporting faunal turf. The area of each habitat potentially directly impacted by the met mast foundation is estimated as 178m 2, plus a limited scour area, which in the context of the amount of each habitat surveyed would constitute an impact negligible in scale. One of the potential met mast locations lies within an area identified as prime sand eel habitat (BH08) while the other (BH03) in an area thought to be unsuitable for sandeels (as defined by Greenstreet et al 2010). However, the potential footprint and any associated limited scouring will be negligible in the context of the tens of square kilometres of prime habitat available for sand eels, and consequentially providing feeding resource for other fish, birds and marine mammals, within the Phase 1 area. [30]
8 Summary The key aspects of this application can be summarised as follows: Seagreen wishes to install a met mast at one of two proposed locations within the Phase 1 area of the Firth of Forth Round 3 Zone; The foundations of the proposed met mast will be suction caissons, which will embed themselves into the seabed under pressure when water is removed from the caissons; The preferred installation option for the caisson foundations uses a jack up rig; The jack up rig will use dynamic positioning for a short period of time (up to 4 hours), while the legs of the rig are lowered to the seabed; Installation of the foundation will take up to 2 days, with fitting of the met mast top side taking a further 2 weeks; A number of cetacean species are known to use the site. A stage 1 EPS risk assessment carried out in section 8.1.3 of this report has classified the risk of injury or disturbance to EPS as low, and consequently there is a negligible risk of an EPS offence; A commitment is made to develop mitigation allowing the use of dynamic positioning for the short period required for the preferred jack up installation method or for the longer period required for the DP barge installation method; and Impacts on seabed physical processes and ecology (including sandeel habitat) will be minimal. [31]
9 References JNCC, CCW, and Natural England. 2010. The protection of marine European Protected Species (EPS) from injury and disturbance: Guidance for the marine area in England and Wales and the UK offshore marine area SCOS (2009). (SCOS Report) Scientific Advice on Matters Related to the Management of Seal Populations: 2009. Available at www.smru.st-and.ac.uk. SCOS, 2008 Thompson, C., Bexton, S., Brownlow, A., Wood, S., Patterson, T. Pye, K., Lonergan, M. and Milne, R. (2010). Report on recent seal mortalities in UK waters caused by extensive lacerations October 2010. Sea Mammal Research Unit. SMRU Ltd. (2011a in prep). Cetacean Baseline Characterisation for the Firth of Tay based on existing data: Bottlenose dolphins. SMRU Ltd. SMRU Ltd (2011b in prep). Baseline Characterisation for FTOWDG area based on existing data:pinnipeds. SMRU Ltd. [32]